diff options
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | NEWS | 1 | ||||
| -rw-r--r-- | lib/matrix.rb | 34 | ||||
| -rw-r--r-- | test/matrix/test_vector.rb | 14 |
4 files changed, 47 insertions, 8 deletions
@@ -1,3 +1,9 @@ +Wed Oct 29 11:43:43 2014 Marc-Andre Lafortune <ruby-core@marc-andre.ca> + + * lib/matrix.rb: Generalize Vector#cross_product to arbitrary + dimensions + based on a patch by gogo tanaka [#10074] + Wed Oct 29 11:43:11 2014 Marc-Andre Lafortune <ruby-core@marc-andre.ca> * lib/matrix.rb: Add Matrix#adjucate @@ -155,6 +155,7 @@ with all sufficient information, see the ChangeLog file. along the +num+ -th row or column. * Vector.basis(size:, index:) returns the specified basis vector * Unary - and + added for Vector and Matrix + * Vector#cross_product generalized to arbitrary dimensions * Vector#dot and #cross are aliases for #inner_product and #cross_product * Pathname diff --git a/lib/matrix.rb b/lib/matrix.rb index f7acd9f1fc..f7d75b328f 100644 --- a/lib/matrix.rb +++ b/lib/matrix.rb @@ -1962,14 +1962,36 @@ class Vector alias_method :dot, :inner_product # - # Returns the cross product of this vector with the other. + # Returns the cross product of this vector with the others. # Vector[1, 0, 0].cross_product Vector[0, 1, 0] => Vector[0, 0, 1] # - def cross_product(v) - Vector.Raise ErrDimensionMismatch unless size == v.size && v.size == 3 - Vector[ v[2]*@elements[1] - v[1]*@elements[2], - v[0]*@elements[2] - v[2]*@elements[0], - v[1]*@elements[0] - v[0]*@elements[1] ] + # It is generalized to other dimensions to return a vector perpendicular + # to the arguments. + # Vector[1, 2].cross_product # => Vector[-2, 1] + # Vector[1, 0, 0, 0].cross_product( + # Vector[0, 1, 0, 0], + # Vector[0, 0, 1, 0] + # ) #=> Vector[0, 0, 0, 1] + # + def cross_product(*vs) + raise ErrOperationNotDefined, "cross product is not defined on vectors of dimension #{size}" unless size >= 2 + raise ArgumentError, "wrong number of arguments (#{vs.size} for #{size - 2})" unless vs.size == size - 2 + vs.each do |v| + raise TypeError, "expected Vector, got #{v.class}" unless v.is_a? Vector + Vector.Raise ErrDimensionMismatch unless v.size == size + end + case size + when 2 + Vector[-@elements[1], @elements[0]] + when 3 + v = vs[0] + Vector[ v[2]*@elements[1] - v[1]*@elements[2], + v[0]*@elements[2] - v[2]*@elements[0], + v[1]*@elements[0] - v[0]*@elements[1] ] + else + rows = self, *vs, Array.new(size) {|i| Vector.basis(size: size, index: i) } + Matrix.rows(rows).laplace_expansion(row: size - 1) + end end alias_method :cross, :cross_product diff --git a/test/matrix/test_vector.rb b/test/matrix/test_vector.rb index 4e2bca6ef6..a063d2ca12 100644 --- a/test/matrix/test_vector.rb +++ b/test/matrix/test_vector.rb @@ -169,7 +169,17 @@ class TestVector < Test::Unit::TestCase def test_cross_product v = Vector[1, 0, 0].cross_product Vector[0, 1, 0] assert_equal(Vector[0, 0, 1], v) - v = Vector[1, 0, 0].cross Vector[0, 1, 0] - assert_equal(Vector[0, 0, 1], v) + v2 = Vector[1, 2].cross_product + assert_equal(Vector[-2, 1], v2) + v3 = Vector[3, 5, 2, 1].cross(Vector[4, 3, 1, 8], Vector[2, 9, 4, 3]) + assert_equal(Vector[16, -65, 139, -1], v3) + assert_equal Vector[0, 0, 0, 1], + Vector[1, 0, 0, 0].cross(Vector[0, 1, 0, 0], Vector[0, 0, 1, 0]) + assert_equal Vector[0, 0, 0, 0, 1], + Vector[1, 0, 0, 0, 0].cross(Vector[0, 1, 0, 0, 0], Vector[0, 0, 1, 0, 0], Vector[0, 0, 0, 1, 0]) + assert_raise(Vector::ErrDimensionMismatch) { Vector[1, 2, 3].cross_product(Vector[1, 4]) } + assert_raise(TypeError) { Vector[1, 2, 3].cross_product(42) } + assert_raise(ArgumentError) { Vector[1, 2].cross_product(Vector[2, -1]) } + assert_raise(Vector::ErrOperationNotDefined) { Vector[1].cross_product } end end |